1,2,3,6-tetrahydro-3-methylphthalic anhydride

Endpoint summary

Description of key information

Acute toxicity - Oral: LD50 - >2000 mg/kg
               - Dermal: LD50 - > 2000 mg/kg

Key value for chemical safety assessment

Acute toxicity: via oral route

Link to relevant study records

Reference

Endpoint:

acute toxicity: oral

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

1995-11-28 to 1997-06-05

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Structural similarities of the target substance to the source substances include the (bi)cyclic ring structure with a carboxylic acid anhydride group as the single reactive moiety. For the target substance the bicyclic ring structures contains a double bond at a specific location within the ring and also contains a substituted methyl group at a specific location on the ring structure whereas for the source substance neither the position of the double bond nor the methyl group are specified.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target substance is a specific isomer of the source substance, tetrahydromethylphthalic anhydride (MTHPA), in which neither the location of the double bond nor the methyl substitution are defined. MTHPA, has a stated composition comprising the target substance 1,2,3,6-tetrahydro-3-methylphthalic anhydride (CAS No. 5333-84-6, EC No. 226-247-6) together with tetrahydro-4-methylphthalic anhydride (CAS No. 34090-76-1, EC No. 251-823-9), 1,2,3,6-tetrahydro-4-methylphthalic anhydride (CAS No. 3425-89-6, CAS No. 222-323-8) and 3-cyclohexene-1,2-dicarboxylic anhydride, 4-methyl- (CAS No. 19438-64-3).


3. ANALOGUE APPROACH JUSTIFICATION
Generally, the physical and chemical properties do not show major differences. All the above mentioned cyclic anhydrides have comparable boiling temperatures, low vapour pressure and, from a physiological point of view, similar partition coefficients. Differences in melting point may be explained by the fact that the substances are representing multi-constituent or mono-constituent substances.
The cyclic anhydrides rapidly hydrolyse in contact with water and the methyl substituted cyclic anhydrides appear to show a low potential for biodegradation. Based on their physico-chemical properties the substances are expected to have low bioaccumulation potentials and comparable adsorption/desorption properties. The dicarboxylic acid degradation product arising from hydrolysis is the moiety of concern with respect to effects in the aquatic environment. The substances have a rather a low potential to cause toxicity to water based species including fish, daphnia, algae and microorganisms.
Acute toxicity is low. All of the substances are expected to be highly irritant to the eye and be both skin and respiratory sensitisers and a harmonised classification is in place for these properties (Index No. 607-240-000). The absence of a mutagenic potential has been demonstrated in various guideline in-vitro tests. The outcome of the available mammalian studies conducted by the oral route suggest local effects (irritation of the stomach mucosa) probably arising from pH effects of the di-acid degradation product to be significant.
Due to structural similarities, comparable physical/chemical properties such as the molecular weight, partition coefficient and vapour pressure, the toxicokinetic profile of the registered substance and the potential structural analogue substances are also expected to be comparable in terms of physiological absorption, distribution, metabolism and excretion processes. The carboxylic acid anhydride group which rapidly hydrolyses to form the di-acid once in contact with physiological liquid, mainly determine the fate of the substance within the body. Available toxicokinetic data demonstrate that cyclic anhydrides are commonly metabolised to the corresponding di-carboxylic acids within the body and are finally excreted in urine.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 401 (Acute Oral Toxicity)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

no

Species:

rat

Strain:

Crj: CD(SD)

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles river Japan
- Age at study initiation: purchase at 5 weeks old. Study is initiated at 6 weeks old
- Weight at study initiation: male 172.1-193.1g, female 125.4-139.9g
- Fasting period before study: from 17:00 on before day to 3 hours following dosing
- Housing:2-3 animals in polycarbonate cage with wood tip
- Diet (e.g. ad libitum): ad libitum
- Water (e.g. ad libitum):ad libitum
- Acclimation period:1 week


ENVIRONMENTAL CONDITIONS
- Temperature (°C): 22-26°C
- Humidity (%): 45-65%
- Air changes (per hr): 13 times/hour
- Photoperiod (hrs dark / hrs light): 12/12 AM07:00-PM07:00

Route of administration:

oral: gavage

Vehicle:

other: corn oil (10ml/kg)

Details on oral exposure:

VEHICLE
- Concentration in vehicle: 5, 10 and 20 w/v% in vehicle
- Amount of vehicle (if gavage):10mL/kg
- Justification for choice of vehicle: Corn oil is generally used
- Lot/batch no. (if required): V5P5523 Nakalai Tesque

MAXIMUM DOSE VOLUME APPLIED: 10mL/kg

CLASS METHOD
- Rationale for the selection of the starting dose: From results of prestudy (500, 1000 and 2000mg/kg p.o.). All animals did not die. at 2000mg/kg the body weight is decreased.

Doses:

0(Vehicle), 500, 1000 and 2000 mg/kg/day (in corn oil)

No. of animals per sex per dose:

5

Control animals:

yes

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: observation: more than one time/day. weighing: day 0, 2, 4, 6, 8, 11 and 15.
- Necropsy of survivors performed: (yes)/no
- Other examinations performed: clinical signs, body weight, organ weights, histopathology, other: histopathology: In representative case,
histopathology observation was performed on stomach.

Statistics:

average and standard deviation (weight, per group)

Preliminary study:

From results of pre-study (500, 1000 and 2000 mg/kg p.o.). All animals did not die. at 2000 mg/kg the body weight is decreased.

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Mortality:

No deaths prior to schedule termination.

Clinical signs:

other: Hypoactivity, bradypnea and prone position were observed in males and females of the 2000 mg/kg group on the day of administration.

Gross pathology:

At necropsy, thickening of the forestomach mucosa was observed in males and females of the 1000 and 2000 mg/kg group.
Adhesion of forestomach and liver was noted in one female of the 2000 mg/kg group.

Other findings:

Histopathology:
Squamous hyperplasia and granulomatous inflammation in submucosa of the forestomach were observed, and a squamous hyperplasia was also noted.
Squamous hyperplasia of the forestomach
1000mg/kg : male (2/5), female (1/5)
2000mg/kg : male (5/5), female (5/5)
(Squamous hyperplasia and granulomatous inflammation was observed in representative case of in males and females of the 1000 and 2000mg/kg group)
Adhesion of forestomach and liver and a foreign body granuloma in the adhesion area
2000mg/kg : female (1/5)

Interpretation of results:

GHS criteria not met

Conclusions:

Oral LD50 values were >2000 mg/kg for rat. The major toxicity was squamous hyperplasia of the forestomach.

Executive summary:

In this study, tetrahydromethylphthalic anhydride (MTHPA), was studied for oral toxicity in rats in a single dose toxicity test at doses of 0, 500, 1000 and 2000 mg/kg for both sexes. Methods followed those described in OECD test guideline No. 401. No deaths occurred of either males or females. Clinical signs of hypoactivity, bradypnea and prone position were observed in males and females of the 2000 mg/kg group on the day of administration. Decrease of body weights was observed in males of the 2000mg/kg group and suppression of body weight gain was observed in females of the 2000mg/kg group on the day of administration. At necropsy, thickening of the forestomach mucosa was observed in males and females of the 1000 and 2000 mg/kg groups most likely caused by the irritative properties of the test substance. Adhesion of forestomach and liver was noted in one female of the 2000 mg/kg group. Histopathologically, squamous hyperplasia and granulomatous inflammation in submucosa of the forestomach were observed in the 1000 and 2000 mg/kg groups. A foreign body granuloma in the adhesion area was also noted in the female of the 2000 mg/kg group. As the result, LD50 value was in excess of 2000 mg/kg.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Acute toxicity: via inhalation route

Endpoint conclusion

Endpoint conclusion:

no study available

Acute toxicity: via dermal route

Link to relevant study records

Reference

Endpoint:

acute toxicity: dermal

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Study period:

from 1993-08-04 to 1993-08-18

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Justification for type of information:

1. HYPOTHESIS FOR THE ANALOGUE APPROACH
Structural similarities of the target substance to the source substances include the (bi)cyclic ring structure with a carboxylic acid anhydride group as the single reactive moiety. For the target substance the bicyclic ring structures contains a double bond at a specific location within the ring and also contains a substituted methyl group at a specific location on the ring structure whereas for the source substance neither the position of the double bond nor the methyl group are specified.


2. SOURCE AND TARGET CHEMICAL(S) (INCLUDING INFORMATION ON PURITY AND IMPURITIES)
The target substance is a specific isomer of the source substance, tetrahydromethylphthalic anhydride (MTHPA), in which neither the location of the double bond nor the methyl substitution are defined. MTHPA, has a stated composition comprising the target substance 1,2,3,6-tetrahydro-3-methylphthalic anhydride (CAS No. 5333-84-6, EC No. 226-247-6) together with tetrahydro-4-methylphthalic anhydride (CAS No. 34090-76-1, EC No. 251-823-9), 1,2,3,6-tetrahydro-4-methylphthalic anhydride (CAS No. 3425-89-6, CAS No. 222-323-8) and 3-cyclohexene-1,2-dicarboxylic anhydride, 4-methyl- (CAS No. 19438-64-3).


3. ANALOGUE APPROACH JUSTIFICATION
Generally, the physical and chemical properties do not show major differences. All the above mentioned cyclic anhydrides have comparable boiling temperatures, low vapour pressure and, from a physiological point of view, similar partition coefficients. Differences in melting point may be explained by the fact that the substances are representing multi-constituent or mono-constituent substances.
The cyclic anhydrides rapidly hydrolyse in contact with water and the methyl substituted cyclic anhydrides appear to show a low potential for biodegradation. Based on their physico-chemical properties the substances are expected to have low bioaccumulation potentials and comparable adsorption/desorption properties. The dicarboxylic acid degradation product arising from hydrolysis is the moiety of concern with respect to effects in the aquatic environment. The substances have a rather a low potential to cause toxicity to water based species including fish, daphnia, algae and microorganisms.
Acute toxicity is low. All of the substances are expected to be highly irritant to the eye and be both skin and respiratory sensitisers and a harmonised classification is in place for these properties (Index No. 607-240-000). The absence of a mutagenic potential has been demonstrated in various guideline in-vitro tests. The outcome of the available mammalian studies conducted by the oral route suggest local effects (irritation of the stomach mucosa) probably arising from pH effects of the di-acid degradation product to be significant.
Due to structural similarities, comparable physical/chemical properties such as the molecular weight, partition coefficient and vapour pressure, the toxicokinetic profile of the registered substance and the potential structural analogue substances are also expected to be comparable in terms of physiological absorption, distribution, metabolism and excretion processes. The carboxylic acid anhydride group which rapidly hydrolyses to form the di-acid once in contact with physiological liquid, mainly determine the fate of the substance within the body. Available toxicokinetic data demonstrate that cyclic anhydrides are commonly metabolised to the corresponding di-carboxylic acids within the body and are finally excreted in urine.

Reason / purpose for cross-reference:

read-across source

Qualifier:

according to guideline

Guideline:

OECD Guideline 402 (Acute Dermal Toxicity)

Version / remarks:

1981

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method B.3 (Acute Toxicity (Dermal))

Version / remarks:

84/449/EEC

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test type:

standard acute method

Limit test:

yes

Species:

rat

Strain:

Sprague-Dawley

Sex:

male/female

Details on test animals or test system and environmental conditions:

TEST ANIMALS
- Source: Charles River (UK) Ltd., Manston, Kent, U.K.
- Females nulliparous and non-pregnant: yes
- Age at study initiation: 10 - 14 weeks
- Weight at study initiation: males - 234-255 g; females - 207-237 g
- Fasting period before study: n/a
- Housing: Individually during the 24-hour exposure period and in groups of up to five, by sex, for the remainder of the study.
- Diet: R&M No. 1, Special Diet Services Limited, Witham, Essex, U.K., ad libitum
- Water: Municipal supply, ad libitum
- Acclimation period: at least 5 days

ENVIRONMENTAL CONDITIONS
- Temperature (°C): 19-22°C
- Humidity (%): 50-56%
- Air changes (per hr): 15
- Photoperiod (hrs dark / hrs light): 12/12

IN-LIFE DATES: From: 1993-08-04 To: 1993-08-18

Type of coverage:

semiocclusive

Vehicle:

unchanged (no vehicle)

Details on dermal exposure:

TEST SITE
- Area of exposure: ca. 5 x 4 cm
- % coverage: ca. 10%
- Type of wrap if used: semi-occluded

REMOVAL OF TEST SUBSTANCE
- Washing (if done): yes - distilled water
- Time after start of exposure: 24 hours

TEST MATERIAL
- Amount(s) applied: 1.68 mL/kg bodyweight giving a dose level of 2000 mg/kg body weight
- Constant concentration used: yes - undiluted
- For solids, paste formed: yes/no

Duration of exposure:

24 h

Doses:

2000 mg/kg bw (1.68 mL/kg bw)

No. of animals per sex per dose:

5

Control animals:

no

Details on study design:

- Duration of observation period following administration: 14 days
- Frequency of observations and weighing: observed for deaths or overt signs of toxicity 0.5, 1, 2 and 4 hours after dosing and subsequently once daily for 14 days. Examined for any dermal reactions after removal of the dressings and subsequently once daily for the remainder of the study. Bodyweight recorded Days 0, 7 and 14.
- Necropsy of survivors performed: yes

Preliminary study:

no preliminary study

Sex:

male/female

Dose descriptor:

LD50

Effect level:

> 2 000 mg/kg bw

Sex:

male/female

Dose descriptor:

LD0

Effect level:

2 000 mg/kg bw

Mortality:

There were no deaths.

Clinical signs:

other: No signs of systemic toxicity were noted during the study. Dermal Reactions: Very slight to well-defined erythema was noted at the treatment sites of all animals one day after dosing with very slight erythema in all females two days after dosing. Haemorr

Gross pathology:

No abnormalities were noted at necropsy.

Other findings:

none

Interpretation of results:

GHS criteria not met

Conclusions:

The acute dermal median lethal dose (LD50) of the test material, tetrahydromethylphthalic anhydride, in the Sprague-Dawley strain rat was found to be greater than 2000 mg/kg bw.

Executive summary:

The study was performed to assess the acute dermal toxicity of the test material in the Sprague-Dawley strain rat. The method used followed that described in the OECD Guidelines for Testing of Chemicals (1981) No. 402 "Acute Dermal Toxicity" referenced as Method B.3 in Commission Directive 84/449/EEC (which constitutes Annex V of Council Directive 67/548/EEC).

A group of ten animals (five males and five females) was given a single 24-hour, semi-occluded dermal application to intact skin at a dose level of 2000 mg/kg bw. The animals were observed for fourteen days after the day of treatment and were then killed for gross pathological examination.

There were no deaths. No signs of systemic toxicity were noted during the study. Very slight to well-defined erythema was noted at the

treatment sites of all animals. Other skin reactions noted were haemorrhage of the dermal capillaries and crust formation. Treatment sites appeared normal two to five days after dosing. All animals showed expected gain in bodyweight during the study. No abnormalities were noted at necropsy.

The acute dermal median lethal dose (LD50) of the test material in the Sprague-Dawley strain rat was found to be greater than 2000 mg/kg bodyweight.

Endpoint conclusion

Endpoint conclusion:

no adverse effect observed

Dose descriptor:

LD50

Value:

2 000 mg/kg bw

Additional information

Various studies have been undertaken on tetrahydromethylphthalic anhydride (MTHPA). This is a structural analogue of 3 -MTHPA D4 in which the methyl substitution is not defined or fixed in a specific position on the carbon cyclic structure, as opposed to 3 -MTHPA D4 where the methyl substitution is fixed at the 3C position. 3 -MTHPA D4 is regarded as a specific isomer of MTHPA.

Oral:

Different studies were available investigating acute oral toxicity of tetrahydromethylphthalic anhydride (MTHPA). The study by Furukawa (1997) was chosen as key study, as this is the only study which was conducted according to a recognised test guideline (OECD 401) and GLP. LD50 values of the supporting studies are in the same concentration range as the key study (some slightly below) but are regarded as less reliable than the key study.

In the key study MTHPA was studied for oral toxicity in rats in a single dose toxicity test at doses of 0, 500, 1000 and 2000 mg/kg for both sexes. No deaths occurred of either males or females. Clinical signs of hypoactivity, bradypnea and prone position were observed in males and females of the 2000 mg/kg group on the day of administration. Decrease of body weights was observed in males of the 2000mg/kg group and suppression of body weight gain was observed in females of the 2000mg/kg group on the day of administration. At necropsy, thickening of the forestomach mucosal was observed in males and females of the 1000 and 2000 mg/kg groups. Adhesion of forestomach and liver was noted in one female of the 2000 mg/kg group. Histopathologically, squamous hyperplasia and granulomatous inflammation in submucosal of the forestomach were observed in the 1000 and 2000 mg/kg groups. A foreign body granuloma in the adhesion area was also noted in the female of the 2000 mg/kg group. As the result, LD50 value was decided as >2000 mg/kg.

In a supporting acute oral toxicity study (Irie, 1969a), groups of T23-48:Donryu rats (6/sex) were given a single oral dose of MTHPA in olive oil at doses of 1160, 1390, 1660, 2000 and 2400 mg/kg bw and observed for 7 days. Oral LD50 = 2102 mg/kg bw

In a supporting acute oral toxicity study (Irie, 1969b), groups of dd mice (10/sex) were given a single oral dose of MTHPA in olive oil at doses of 920, 1100, 1330, 1590, 1900, 2280, 2720 mg/kg bw and observed for 7 days. Oral LD50 = 1707 mg/kg bw

In a supporting acute oral toxicity study (Sheena, 1980), groups of Crj: CD(SD) rats (105/sex) were given a single oral dose of MTHPA in olive oil at doses of 1000, 1600, 2000, 3200, 5000 and 6400 mg/kg bw and observed for 14 days. Oral LD50 = 1900 mg/kg bw (1600-2900 mg/kg bw)

In a supporting acute oral toxicity study, groups of rats were given a single oral dose of MTHPA. Oral LD50 = 25894 mg/kg bw

Inhalation:

No data are available regarding acute toxicity by the inhalation route. In accordance with REACH Regulation 1907/2006 (Annex VIII, Column 2), testing by the inhalation route (required in section 8.5.2) does not need to be conducted as the physico-chemical properties the test substance do not indicate significant distribution into the air in particulate or vapour form.

Dermal:

A single study study is investigating acute dermal toxicity of tetrahydromethylphthalic anhydride (MTHPA). The method used followed that described in OECD/EU test methods.A group of ten animals (five males and five females) was exposed on intact skin to a dose level of 2000 mg/kg body weight for a 24 hour period. There were no deaths and no signs of systemic toxicity noted. Local effects (irritation) were noted at thetreatment sites of all animals. The median lethal dose (LD50) was in excess of 2000 mg/kg.

Justification for classification or non-classification

Based on the results obtained in the acute toxicity studies (oral: LD50 (rat) > 20000 mg/kg bw; dermal LD50 (rat) > 2000 mg/kg bw) and taking into account the provisions laid down in Council Directive 67/548/EEC and CLP (1272/2008/EC), no classification is required regarding acute toxicity.